It has been known to utilize various phosphorous containing materials as additives to polyester polymers to provide fire retardancy. For practical utility, however, it is not only necessary that the polymer composition be fire retardant, but it is also necessary that the polymer composition can be processed into various sized fiber and/or filament, that the product be readily dyeable and that the additive remain in the processed product during its useful life. Many of the phosphorous containing materials heretofore employed to render polyester compositions fire retardant have had phosphorous contents of about 14% or less, thus relatively large amounts of the phosphorous containing materials were necessarily employed to obtain acceptable flame retardance. In addition, perhaps because of relatively low melting points it has been observed that in some instances phosphorous containing materials were lost from fiber or filament during normal processing at elevated temperatures.
It is pointed out that certain cyclophosphazene phenyl and phenoxy derivatives and their use as fire retardant additives in polyester fibers and filaments are described in U.S. Pat. Nos. 3,865,783 and 3,859,249. In addition, Japanese application 69 6177, Chem. Abstracts, 77:115968d teaches there was a triphosphonitrilehexakis(di-Na phosphoxyethylamide) and the like as a textile fire resistant treatment.
The preparation and characterization of various phosphazene additives and/or chemistry that can be used or adapted for use in the practice of this invention are presented in, for example, Chemical & Engineering News, Apr. 22, 1968, pages 68-81 (H. R. Allcock) and U.S. Pat. Nos. 3,304,350; 3,732,316; 3,928,463 and 4,020,110. The preparation of certain organophosphorous polymers and their use as flame retardants is set forth in the following representative art U.S. Pat. Nos. 2,891,915; 3,193,397; British Pat. No. 1,208,748; Chemical Reviews, 62: 247-281 (1962); J.A.C.S., 80: 2116 (1958) and Inorg. Chem., 3: 428 & 594 (1964); see also the art cited therein, i.e. U.S. Pat. Nos. 2,853,517; 3,280,222; 3,316,330; 3,322,859; 3,356,769; 3,392,214; 3,450,799; 3,446,763; 3,505,087; 3,624,024; 3,629,365 and 3,792,117.
Polyphosphazene polymers containing repeating ##STR1## units in which various substituted and unsubstituted alkoxy, aryloxy, amino and mercapto groups are attached to the phosphorus atom and their method of preparation are described in the prior art as illustrated in the publication "Nitrogen-Phosphorus Compounds", Academic Press, New York, N.Y., 1972 by H. R. Allcock and "Poly(Organophosphazenes)", Chemtech, Sept. 19, 1975 by H. R. Allcock and in such U.S. Pat. Nos. as 3,515,688; 3,702,833, 3,856,712, 3,974,242, and 4,042,561 the disclosures of which are herein incorporated by reference.